Bnstow and Whitaker — On the Chesil Bank. 437 



until it reached the next stream. This might take place with 

 several streams, where two were near together, and the increased 

 force of two united would give the resultant stream greater power 

 to continue its eastward course and to join on to the next. The 

 consequence of the continuance of this process would be, that all 

 the streams would at last join to form one long channel between 

 the beach and the mainland, as in the subjoined Woodcut, which 

 is on a larger scale than the Map (Plate XIV.), with the streams 

 continued to the beach. 



MW. 



Sea 



Plan of streams flowing to a shore where there is a current chiefly in one direction. 



It seems well within the limits of possibility that this body of 

 water would have pov/er enough to keep its channel free, and to 

 prevent the firm compact shingle from being driven back against the 

 mainland. In this case the land would be protected from the cliff- 

 forming action of the sea, but on the other hand would be subject to 

 the scooping action of land-waters, which would cut it back in 

 gentle slopes, and irregularly widen the channel, according to the 

 nature and hardness of the different beds acted on. 



Of course, on any theory, the Chesil Bank could not have been 

 formed but for the existence of the natural breakwater of Portland ; 

 and, according to the theory now brought forward, either the naiTOW 

 neck of land which must once have connected Portland with the 

 mainland, has been breached by some means or other, inwards 

 towards Weymouth Bay (instead of the beach being breached out- 

 wards to the sea) ; or, on the other hand, if at first the beach was 

 broken through, and the stream flowed out to the sea in a southerly 

 direction, that breach must have been slight enough to have been 

 filled by the heaping up of shingle, when the land in its rear was 

 worn away and Portland was separated from the mainland. As the 

 connecting isthmus must have consisted of Kimmeridge Clay, its 

 destruction would be no hard matter to the sea on one side (N.), 

 and the stream on the other ; and as large breaches in the Chesil 

 Bank are known to have been refilled in a very short time, there is, 

 perhaps, no great difficulty in accounting for the phenomena on 

 either supposition. . 



The destruction of the land between Portland and the mainland 

 on the north, has been made easier by the beds having been thrown 

 into a sort of arch, with a shai-p northerly and a gentle southerly 

 dip ; the arch being of course tlie form that helps denudation, both 

 by fissuring the beds, and by giving them a tendency to fall out- 

 wards. In this particular case, moreover, the lower beds that have 

 been brought to a higher level by the said arch, so as to be within 



